On a possible method to measure the radial profile of the photoelastic constant in step-index optical fiber

We describe a measurement method to determine the radial distribution of the photoelastic coefficient C in a step-index optical glass fiber. This method is based on the measurement of the retardance profile of a transversally illuminated fiber for increasing tensile load. The radial profile C(r) is obtained from the inverse Abel transform of this retardance profile. We measured three step-index glass fibers with three different core radii The results suggest that C may be constant across the fiber section and that the mean absolute value of C is slightly larger for glass fibers than for fused silica. Additionally, the shape of the actual refractive index profile can be derived from the retardance measurements.